Although the three windows are actually aligned vertically, the central window appears shifted to the right, in the direction of the drifting dots that it contains.
Eight circular windows, arranged in a circle, contain random dot textures that move counterclockwise. Although the windows themselves are not moving, they appear to rotate together like a ferris wheel. This is a stronger version of the illusion demonstrated above — it introduces continuous illusory movement, not just a static illusory shift. Also, after fixating for a while, you may perceive the windows fade out and disappear.